Ships leaving the easternmost port of Estonia, Sillamae, began to choose the most dangerous route. They go through the shoals in the territorial waters of the country to enter the international transport corridor in the neutral waters of the Gulf of Finland.

Baltic nations have sounded the alarm about Russia's increasing aggression in the region including suspected acts of sabotage. Last week, Estonia accused Russia of violating NATO airspace with a fighter jet when Tallinn tried to intercept a suspected "shadow fleet" vessel in the Baltic Sea.

Estonia will keep checking Russian "shadow fleet" vessels, Prime Minister Kristen Michal told Reuters on Sunday, days after Russia deployed a SU-35 fighter jet as Estonia attempted to alter the course of one such ship.